1. Field of the Invention
The present invention relates to a monolithic assembly of a fast diode and an IGBT transistor.
2. Discussion of the Related Art
In many circuits, component connections of the type illustrated in FIG. 1 including a MOS power transistor having its drain connected to the anode of a diode can be found. This configuration is notably found in booster circuits such as those used in a.c./d.c. or d.c./d.c. converter circuits. In such applications, the MOS transistor must be able to withstand a relatively high voltage and the diode has to be very fast.
This raises integration problems. Indeed, FIG. 2 shows, in its left portion, a conventional structure of a cell of a vertical MOS transistor and, in its right portion, a conventional structure of a vertical diode. In FIGS. 1 and 2, the gate, the source, and the drain of the MOS transistor, and the cathode of the diode have been referred to by the same references G, S, D, and K, respectively.
For the diode to be fast, its substrate N is doped with gold or platinum or is submitted to another process to increase its speed. Such processes are difficult to perform on a portion of the component only. Thus, if a single component integrating the diode and the MOS transistor is implemented, the processing to increase the speed of the diode reduces the voltage withstanding ability of the high voltage MOS transistor and increases the value of its on-state resistance.